1. Field of the Invention
The invention relates to a semiconductor apparatus and more particularly to a wet etching apparatus with an automatic filter cartridge cleaning function.
2. Description of the Related Art
Wet etching is a standard process in the semiconductor industry. FIG. 1 shows a wet etching apparatus 100 for etching glass substrates of TFT-LCD. The apparatus 100 includes etching tanks 102, and 104, each with a capacity of 150 liters, containing an etching solution 10, supply the etching solution 10 to a reaction tank 122 through a duct assembly system, and recycling the etching solvent 10 to etching tanks 102 and 104 with a recycling system (not shown). The above-mentioned duct assembly system further comprises a pump 162, driving the etching solution 10 through the duct assembly system, valves 131 and 132, controlling the flow of etching solution 10 from the etching tanks 102 and 104 respectively, a valve 133, controlling the flow of etching solution 10 from the pump 162, filters 111 and 112, containing one or a plurality of filter cartridges 117 to filter impurities resulted from the etching solution, valves 134 and 135, controlling the flow of etching solution 10 into the filters 111 and 112 respectively, and valves 136 and 137, controlling the flow of etching solution 10 from the filters 111 and 112 into the reaction tank 122 respectively. The etching tanks 106 and 108, each with a capacity of 270 liters, containing etching solution 10 therein, supply etching solution 10 to reaction tanks 124 and 126 respectively or simultaneously by the duct assembly system. The structure of the duct assembly system, supplying etching solution 10 to reaction tanks 124 and 126, is similar to above described duct assembly system hence its description is omitted here. Moreover, the duct assembly system may employ one or more filters. The advantage of the wet etching apparatus 100 is that it contains two filters 111 and 112, and the valves 134, 135, 136, and 137 are controlled to filter the etching solution 10 by a filter 112 during cleaning, repairing, and maintaining the filter 111. Additionally, the etching apparatus 100 can be cleaned, repaired and maintained without being shut down.
When etching a SiOx/SiNy layer on a glass substrate, the SiOx/SiNy layer is sprayed with or soaked in the etching solution 10, such as BFH (HF+NH4F+ surfactant), to cause a reaction. When etching the glass substrate in the reaction tanks 122, 124 and 126, reactants and air bubbles are produced during the chemical reaction mentioned above. As the etching solution is recycled, reactants and air bubbles will adhere to the filter cartridge 117 causing it to jam during chemical reaction, after producing 80˜200 glass substrates.
The reactants jamming the filter cartridge 117 cannot be dissolved by water with low solubility, and the bubbles will only gradually disappear over time, hence, the filter cartridge 117 must be cleaned by manually injecting water into the filters 111 and 112 continuously, after producing about 80˜200 glass substrates.
Another disadvantage of the conventional method described above, is the manual operation of control valves. The reduction of concentration of the etching solution results from the water injecting into the reaction tanks 122, 124, or 126 and further causing the etching rate of SiOx/SiNy layer on the glass substrates to be abnormal during the etching reaction. As: a result, an excess of glass substrates are wasted due to substandard quality, increasing manufacturing costs, and reducing throughput. Moreover, the manpower required by manual operation also increases costs. Additionally, the filter cartridge 117 cannot be effectively cleaned during a production run as the warning system of the conventional apparatus is not activated until the filter cartridge 117 is completely jammed. Due to this, it is difficult to inject water into the filter cartridge 117 to clean the filter in timely manner, and a new filter cartridge 117 must be installed resulting in downtime, decreased throughput, and increased material costs.